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Triumph TR6 - supercharged TR6 cam
|Call me lazy, but I would like to know if anyone can tell me what cam would be best to use when supercharging a TR6 engine? I am now in the process of re-starting my stalled project. Dropped the engine off at the machine shop today. Will have to have a new cam and followers. It is a 74 model engine, with standard bore, no plans to race or anything like that, only to drive aggressively. 2000-5000 RPM range.|
|From what I understand when you run boost on an engine, you do not want to run a NA "hot" cam. It has to do with valve overlap, unfortunatly that is all I can remember.|
|Agree with crj, mostly!|
You want to avoid a very long duration cam because the overlap will mean that as the supercharger pushes more mixture into the engine a lot of it will escape past the still partly open exhaust valve.
But I see no reason why greater lift would not give some benefit.
|From the rpm range that you mention, probably the best camshaft for the application is......a stock cam from a 1974 TR6. The same cam was used for the late carb and late PI engines. Going back to the engine models that we built some time back when all else was left the same except camshaft, that camshaft was the best over your stated range. |
The early carb cam resulted in slightly higher horsepower below 4000 rpm, but things had crossed over to the late carb/PI cam by 4000 rpm. The Reed XS252 grind was slightly better up to about 4500 rpm, but had dropped back by 5000 rpm. Note that both the stock cam and the Reed XS252 are 252 degree of duration cams, but the Reed cam has less overlap (32 vs 36 degrees) than the stock cam due to different valve opening and closing points. Stock cam advantage is that it is a stock cam and can be purchased new while the Reed is a regrind of a stock cam. Reed cam advantage is that the regrind price is less than the cost a new stock cam assuming that you have a grindable core.
Everything else, different Reed grinds, different APT grinds, Kent, Isky, Triumph S2 grind all made higher numbers by 5000 rpm and above, but produced lower numbers below 4000 rpm in the various models. This was true even when the models were tweaked by advancing the cam up to 2 degrees in order to "bring it in" at a lower rpm.
|I occasionally would like to take my motor to 6k but don't want to throw anything out the bottom. Realisticly only drive in the rpm's stated. Would love more but.. Anyway, the engine I am building is a 74 model but one of the cam journals was gaulded badly. Cam ruined, am having cam bearings installed. Looking forward to this though.|
|Hi Gene, There are so many variables that have to be considered with a cam recommendation - don't rush to judgement. I've been very happy using a new stock 125HP cam - from Newman cams in England in my '75. (Steve's point above) I'm also using high lift roller rockers - a 1.6 to 1 set currently, that provide more 'pop' without sacrificing any low end power. (Simon's point above) The engine is very docile at low revolutions and happily chugs along , then snorts pretty good up to my 'chosen' redline of 5000rpm. I'm sure it would pull happily to 6000, but I don't see the need. On the dyno it makes 127HP at the rear wheels (5000rpm) or approximately 180HP at the crank. (175 foot pounds of torque -- a very flat curve too !!)|
Jetting is still on the lean side , so I expect more power this summer after more carb and ignition tuning. Since you'll have good ,new cam bearings a higher rocker ratio could be an option too. I have 1.75 to 1 rockers that worked fine before the complete rebuild and blower installation last winter -- I'm going to try them this summer. If you keep revs relatively low (under 5000) most of the time, I'd suggest using a relatively soft set of valve springs from BPNW (for stock motors - about 50 pounds/inch) - so that valve, cam bearing, and push rod wear is minimized - and, no signs of valve float. My compression ratio is 7.7 to 1.
Obviously, a well ground cam with stock duration and higher lift would work just as well, others have gone this path. Getting rid of the stock rockers does offer some benefits - I like the idea of reduced valve and valve guide wear,they're quieter plus they look so cool! Have fun -
|I already have a set of 1.7:1 roller rockers on my stock engine. This engine is a spare that I am building just for this supercharger project. I also have EFI so jetting will be tuned when run in is achieved. I just want to make sure that I don't leave any HP on the table so to speak by using the wrong cam. I've had too aggressive of a cam before and it was great as long as I kept the rpms up but really not that practical. I also have a aluminum flywheel for this engine. I also intend to focus on clearances on my valve stem/guides as well as use the total seal rings in an effort to reduce blowby. I occasionally take my engine to 6k but all it does is make noise at that engine speed.|
|If the ante is upped to 6000 rpm, then the options open up a bit. The Reed XS266 passes the late PI/late carb cam on the curves just over 3000 rpm and is just starting to drop off at 6000. The Isky Z-19 crosses curves at about 3600-3700 rpm and peaks out at 6000. The APT TH56N is pretty much between the Reed XS266 and the Isky Z-19. The Reed XS270 is a little hotter than the Isky Z-19. The XS270 comes in a little earlier than the Triumph S2 grind, they both peak very close together, but the XS270 drops off faster by 6500 rpm. Overall the S2 is a little down on power and torque compared to the other modified cams. The early PI cam tracked the S2 but was a step behind on the curves. The real disappointment when we were building the models was the Kent 17-161 cam. It was late coming in compared to others and was only marginally higher in peak power than the stock late PI/late carb cam, and worse by far on the torque curves. Go figure.......|
|I was informed yesterday that MOSS has in the works a supercharger for the TR6. They already have it for the MG.|
|Rick, can you give more info? can't find it on Moss' site.|
|Moss has been working on an Eaton M62 Supercharger set-up "kit" using a single HIF carb (as I recall). It's supposed to |
be available "this summer", probably. They're using Jackson Racing as the development team . It's not yet available, and it may be "awhile". Call and talk to on their "tech experts" phone line --they'll know. I've looked at the MGB set-up and it's nicely designed , the TR6 should be the same. No ,coming from Moss, it won't be cheap.
|As far as price on superchargeing, believe me, cheap never fits in. I am using one of the rootes s/cs of of a Toyota previs 2.4 liter engine. With the supercharger, machining, EFI parts and all, I bet I am up to 5-5500 range now with a couple or three thousand more to go. |
Steve P., thanks for all this info. How is drivability around town on the REED XS266? I understand that the lower inertia of the aluminum flywheel affects pulling off a little, and then power in the 3-6K range sounds like I may be sorry. I drive my car mostly around town and to shows. But, I like the idea of a cam that will allow me to pull to 6k if I want to.
Oh yeah, I am putting an intercooler on as well with my s/c project.
|The cam doesn't present a problem. If you get stuck in a lot of stop and go, you actually get more problem out of the aluminum flywheel. In the models, the strongest of the bunch at 3000 rpm is the early carb cam, followed by the Reed XS252, the late PI/late carb and the XS266. At 3500 rpm it was the Reed XS252, with the late PI/late carb cam and the early carb cam just behind. After that the early carb cam drops out of the picture. The XS266 is just behind those two. Torque curves follow the same pattern|
At 4000 rpm, the XS252, XS266 and late PI/late carb cam on all on top of each other on both the power and torque curves. At 4500 rpm, the XS266 takes the lead for these three, with the XS252 and late PI/late carb cam on top of each other on both curves. By this point the Isky z-19, the XS270 and the two APT cams start to match or exceeed the three cams under discussion.
At 5000 rpm, the XS266 has taken a clear lead over the other two, with the late PI/late carb cam over the XS252. By 5500 rpm, the lead has grown for the XS266, while the late PI/early carb cam has also incresed its lead over the XS252. At 6000 rpm, you have run past the peak power and torque for all three cams. The XS266 has just started to drop off, while the other two are well down the curve from their peaks.
When we were doing all of these models, I was thinking in terms of a street car and piston speeds. With the long stroke of the TR6 engine, this essentially means a reasonably low redline. Using a piston speed of 3500 ft/min as as baseline yellow zone bottom end, this took me out to about 5600 rpm. Then for the occasional excursion to 3800 ft/min, I got out to about 6100 rpm. Thinking street rpm and some occasional rip snorting, the target range for me was the 3000 to 5500 rpm.
|That sounds like what I want to do as well. After getting my s/c project sorted through, I hope to do the Richard Good conversion of the diff to the Nissan diff with 4.09:1 gears. That should help the low end take offs. And I have o/d so I'm not too worried about turning too high of rpms on the highway.|
|I use a bog standard late TR6 (125bhp) cam. I would fit roller rockers but need to cure fall-off in boost above 3000rpm first. I think that's due to restriction from either the single 2"SU or the cramped outlet on the blower manifold. I suspect if you gear the blower to give 6psi at 3000rpm then the stock cam will give enough excitement for road work. The effect of the blower on the stock motor is so dramatic that fine-tuning becomes almost unecessary- or maybe I am getting too old and slow... |
Good to hear Moss are into blowing TR6s.
|P H Cobbold|
|Hi Peter -- on the dyno last September my car was pretty lean (14.0to1) from 3000-5000 when I shut it down, worried about too lean. Joe Curto(the main SU man in the US) is convinced we need an electric fuel pump to provide enough fuel through the SU. His supercharged TD fragmented a piston last fall - so we're both installing a Facet pump this spring. Maybe not enough fuel could be the cause of your drop-off in boost. I'll report back in about a month on this modification.|
I sure like the late cam - as you report - it's incredibly docile and smooth when you want to go slow, and gets with the program when excited.
Spoke with Harry , chief technical man at Moss in the USA on Tuesday and it appears that they are Not in any big hurry to develop the TR6 application after all. Right now they are working on an application for the Midget! He said that after that one is done they are going to start work on a Healey or TR6, but "they haven't decided yet". So, I wouldn't be holdin my breath if you're after a blower.
|David- I'll talk to you about Facet, if your hot to trot on them I'll sell you mine. I am going a different way. We'll talk when I see you.|
I use an electric fuel pump and two float chambers on the SU. The needle has been shaved almost to a point too.
A really weak mixture would not affect boost, but does prevent engine getting up to revs (it feels reluctant to rev) followed a second or so later by holed
|P H Cobbold|
Integral Cams has a TR6 supercharger cam based which was brought about by my discussions with them about five years ago. The LCAs were moved apart a few degrees to decrease overlap and I believe the exhaust profile has more lift&duration than the intake. Specs are on their website. I never ended up using the cam, but Mitch Seff is with his VIS kit.
Hi Peter, nice to see you're still around with that RO34 blown TR6 :)
For anyone else interested, I will be at the TRF Summer Party in August with our company's TR6 Supercharger kit. It will be the debut showing. Using a stock cam though to demonstrate the effectiveness on a dead stock motor.
Kai M. Radicke
* British Car Parts *
|Kai @ Wishbone Classics|
|Thanks Kai, I have e-mailed them for info on ordering.|
I went to the website and could not find the "TR6 Supercharger Kit".
That is because it is not available for purchase yet. The initial outing will be at the TRF Summer Party in August. So the website, which is in need of an extensive redesign anyway, will be updated also in August to reflect the kit's availability then.
This has been a long time in the making. I had a VIS supercharger kit years ago (now owned by James Maddox who has added a custom EFI setup using an Electromotive TEC3 ecu). But the VIS kit, and the copy-cat VIS kits available now, are inadequate in many ways... and I was never fond of the thrown-together appearance.
|Kai @ Wishbone Classics|
Now that you have "spilled the beans" on the supercharger kit coming out, please can you tell us anymore? Is it using the Eaton unit? and does it come with EFI? I was thinking about an Eatom M62 project with the megasquit EFI system. Please tell us more.
This thread was discussed between 19/03/2005 and 05/05/2005
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